4.3.12 Human Pedigrees

4.3.12 Human Pedigrees Drawing and Analysis

Genetic Counseling • Helping individuals and prospective parents • Your learning gives you the opportunity to determine some probabilities and patterns of inheritance yourself!

Determining Risk Probability of inheriting a particular gene is dependent on parents’ genes. Sometimes information about a parent is not enough or unknown. We use genetic information about other family members to help “solve the puzzle” as best as possible

Pedigrees A pedigree is a biologicalfamily tree that shows the interrelationships between parents and children across generations. Helps illustrate a pattern of inheritance for a single trait through that family

Pedigrees

Standard Symbols in Pedigrees Male Female Unspecified Gender

Standard Symbols in Pedigrees Clinically Unaffected Clinically Affected Carrier Not Clinically Affected

Standard Symbols in Pedigrees SB #wk Deceased Still Birth / miscarriage

Conventions in Drawing Pedigrees Parents Regardless of Social Relationship Male partner on left (usually)

Conventions in Drawing Pedigrees I 1 2 II 1 2 3 Full Siblings (in order of age from left to right)

Conventions in Drawing Pedigrees I 1 2 II 1 2 3 4 Monozygotic Twins Dizygotic Twins

Conventions in Drawing Pedigrees I 1 2 3 Separated Blood Relative II Adopted 1 2 3

Patterns of Inheritance • Dominant: • Trait is expressed in every generation • eg. Huntington’s, brown eyes • Not seen in offspring unless present in a parent • Recessive: • Trait may skip generations • eg. TaySachs • Sex-Linked: • Y linked – only males are clinically affected • X linked – affected males may have normal parents, affected females must have affected father

Simple Pedigrees • Pg. 138 DBQ • Pg 140 DBQ • Pg 145 DBQ

Determining Risk Several individuals in Ms. Soule’s family have been diagnosed with either Breast Cancer (BRCA) or Polycystic kidney (PKD). PKD vs. healthy kidney Ms. Soule would like to know what risk she has of developing these conditions.

b) Ms Soule’s Pedigree – Matrilineal/Genetic (1) I have a daughter. I have one sister and she has a son and a daughter. My mother has a sister and a brother. My mother’s sister has two daughters. My mother’s brother has a son and a daughter. My maternal grandmother was second youngest of sisters. (2) The oldest of my maternal grandmother’s sisters had four daughters. The eldest of these had two daughters of her own and she also developed breast cancer. (3) The next of my grandmother’s sisters had one daughter. Her daughter and husband both died from polycystic kidney disease. (4) The youngest of my grandmother’s sisters had two sons. One of those sons had one daughter; the other had one son and a daughter. (5) My grandmother’s mother had a sister. My grandmother’s maternal grandmother died of breast cancer. My maternal grandmother’s mother had breast cancer and so did my grandmother. Two of my grandmother’s sisters had breast cancer (not the one whose family showed polycystic kidney disease). • Which disease should Ms Soule be more worried about PKD or breast CA? • Breast CA has not been seen in Ms Soule’s family in her generation or her parent’s generation. Does that mean she is not at risk? What kind of inheritance is this?

Pedigree Problems a) Ms Soule’s Pedigree – Social I am married to Peter. I have one sister, Lindsay. She is married to Joe and has a (cute!) son, Jeremy. My parents (Doug and Judy) are both alive and still married. My dad is an only child, but my mom has a brother, Pete, and a sister, Becky. 1)Becky was married to Jeff and had two daughters (Amy and Addy) and one miscarriage.2) They divorced and both remarried.3) Jeff’s new wife had a son from a previous marriage and together they had a second son. Becky and her new husband did not have any kids. My uncle Pete married Chris and had a son, Mark, and a daughter, Stephanie. Stephanie is married with two daughters and a son of her own. Pete and Chris divorced, and Pete remarried Barbara, who has one son from a previous marriage. Her son is married and has a son and daughter. My mom’s parents are still alive and married. 4) My dad’s parents divorced, and his mom remarried Joseph who had two children from a previous marriage, but I don’t know if they’re boys or girls.5) My father’s father passed away.

4.3.12 Human Pedigrees